1. Field
The present disclosure pertains to communication devices incorporating multiple Subscriber Identity Modules (SIMs), and more particularly, to techniques that permit hand free devices to manage multiple calls from different SIMs.
2. Background
Communication devices, including mobile/wireless communication devices, mobile phones, smartphones, etc., may include multiple subscriber accounts. For instance, Dual SIM devices (e.g., Dual SIM Dual Standby DSDS, Dual SIM Dual Active DSDA, etc.) permit a communication device to communicate using different subscriber accounts and/or networks. Each SIM may be associated with a different subscriber account, a different network, and/or a radio access technology (RAT).
Many communication devices are adapted with short range or near field wireless communication capabilities to allow the exchange of voice and/or data communications. For example, many mobile phone devices are enabled with Bluetooth interfaces that allow a mobile phone device to send and/or receive audio and/or data to/from a Bluetooth-enabled device. This enables what is commonly referred to as “hands free” operation of a device.
In Bluetooth terminology, a mobile phone is often called an audio gateway (AG) and the wireless headsets or car kits are called often referred to a hands free unit (HF). The AG and HF communicate with each device using standard (Global System for Mobile Communication (GSM) Attention (AT) commands. Only an HF is designed to send any AT commands (e.g., ATA, ATD, AT+CHLD).
Bluetooth Hands free Profile 1.6 (HFP 1.6) is a technical specification designed by Bluetooth SIG https://bluetooth.org. The current Bluetooth Hands free Profile is designed to handle single SIM call scenarios with call states: one active, one held call, and one incoming call (e.g., three calls total) at one instant of time. No additional states beyond this transitory three-call state is possible when using a single SIM. Note that the maximum acceptable final state could be one active and one held (i.e., two calls total).
DSDA devices are able to support up to six (6) calls on two subscriptions. For instance, a first subscription SUB-A may support 1 active call, 1 held call, and 1 incoming call, while a second subscription SUB-B may support 1 active call, 1 held call, 1 incoming call. With these multi-SIM communication devices, no mechanism is currently available to allow a HF device to handle calls from two or more SIMS (subscriptions). That is, this call state (e.g., from multiple SIMs) cannot be conveyed to the HF device with the current Bluetooth HFP specification. Additionally, under the HFP 1.6 specification, no mechanism currently exists to allow conveying subscription information to the HF device from the AG device.
Consequently, there is a need for ways to permit a HF device to select calls in multi-call scenarios, especially in the context of multi-SIM devices.